Trump Jr. says father is 'changed man'

Secret Service protection has been increased for former President Donald Trump, Homeland Security Secretary Alejandro Mayorkas said.

The enhancement is "based on the evolving nature of threats to the former president and his imminent shift from presumptive nominee to nominee," Mayorkas said. "This includes enhancements related to securing the former president during the Republican National Convention this week. I cannot discuss specifics ... as they involve sensitive tactics and procedures. I can say, however, that personnel and other protective resources, technology and capabilities have been added."

"Adjustments" have also been made to President Joe Biden's and Vice President Kamala Harris' protective details, Mayorkas said.

-ABC News' Justin Ryan Gomez

The FBI said it's gained access to suspected gunman Thomas Matthew Crooks' phone and investigators are continuing to analyze his electronic devices.

Searches of Crooks' home and car are complete, the FBI said.

The FBI said it's continuing to investigate the shooting "as an assassination attempt on former President Donald Trump and as potential domestic terrorism."

Nearly 100 law enforcement officials, attendees and other witnesses have been interviewed, the FBI said. "That work continues," the FBI added.

On the day of the shooting, the 20-year-old suspected gunman, Thomas Matthew Crooks, told his father that he wanted to go to the gun range, so his dad let him use his AR-15-style rifle, according to a source familiar with the matter.

Crooks would occasionally go target shooting and use his father's gun, the source told ABC News. Since this wasn't an unusual occurrence, the father didn't think anything of it at the time, the source said.

Crooks recently purchased ammunition both online and in person, the source said.

-ABC News' Mike Levine

Secret Service Director Kim Cheatle will address the GOP-led House Committee on Oversight and Accountability at 10 a.m. on Monday, July 22.

"The United States Secret Service has a no-fail mission, yet it failed on Saturday," committee Chairman James Comer, R-Ky., said in a statement Monday.

"Americans demand answers from Director Kimberly Cheatle about these security lapses and how we can prevent this from happening again," he said.